JP2022094175A - Steering controller - Google Patents

Abstract

To provide a steering controller capable of ensuring a steering reaction force, which serves as information for a driver, even when a current of a steering motor is limited.SOLUTION: A steering reaction force command value arithmetic unit 52 includes an angle axial force arithmetic block 81A, current axial force arithmetic block 81B, and axial force distribution arithmetic block 81C. The angle axial force arithmetic block 81A computes an angle axial force AF1 on the basis of a pinion angle θp. The current axial force arithmetic block 81B computes a current axial force AF2 on the basis of a current value of a turning motor. The axial force distribution arithmetic block 81C mixes the angle axial force AF1 and current axial force AF2 at a predetermined distribution ratio so as to compute a final axial force AF3 that is a final axial force to be reflected on a steering reaction force command value T*. When a specific situation in which the current of the turning motor should be limited takes place, the axial force distribution arithmetic block 81C computes the final axial force AF3 with the distribution ratio of the current axial force AF2 to the final axial force AF3 set to 0% and the distribution ratio of the angle axial force AF1 to the final axial force AF3 set to 100%.SELECTED DRAWING: Figure 3

Description

The present invention relates to a steering control device.

Conventionally, a so-called steer-by-wire type steering device in which power transmission between a steering wheel and a steering wheel is separated is known. This steering device has a reaction force motor that is a source of steering reaction force applied to the steering shaft, and a steering motor that is a source of steering force that steers the steering wheels. When the vehicle is running, the control device of the steering device generates a steering reaction force through a reaction force motor and steers the steering wheel through the steering motor.

In the steer-by-wire type steering device, since the power transmission between the steering wheel and the steering wheel is separated, the road surface reaction force acting on the steering wheel is difficult to be transmitted to the steering wheel. Therefore, it is difficult for the driver to feel the road surface condition as a response through the steering wheel.

Therefore, for example, in the control device described in Patent Document 1, the ideal axial force, which is an ideal rack axial force based on the target steering angle, and the road surface axis, which is an estimated value of the rack axial force based on the current value of the steering motor. Calculate with force. The control device adds up the ideal axial force and the road surface axial force at a predetermined distribution ratio, and controls the reaction force motor using the base reaction force based on the added axial force. Since the road surface condition is reflected in the road surface axial force, the road surface condition is also reflected in the steering reaction force generated by the reaction force motor. Therefore, the driver can feel the road surface condition as a steering reaction force.

Japanese Unexamined Patent Publication No. 2017-165219

The conventional general steer-by-wire type steering device including the steering device of Patent Document 1 is provided with various protection functions according to the product specifications. As an example of the protection function, there is an overheat protection function of the steering motor. The control device having this function monitors the temperature of the steering motor, for example, and limits the amount of current supplied to the steering motor when the monitored temperature approaches an overheated state. This makes it possible to protect the steering motor.

However, when the control device that reflects the road surface axial force in the steering reaction force is provided with the overheat protection function of the steering motor as in Patent Document 1, the following concerns are concerned.
That is, the road surface axial force is calculated by multiplying the current value of the steering motor by a predetermined coefficient. Therefore, when the current amount of the steering motor is limited from the viewpoint of overheat protection of the steering motor, the road surface axial force and eventually the steering reaction force may decrease according to the limited current amount. Therefore, for example, even though the steering reaction force should be increased as information to the driver, the steering reaction force originally required by the overheat protection function of the steering motor cannot be secured. I am concerned.

An object of the present invention is to provide a steering control device capable of ensuring a steering reaction force as information for a driver even when the current of a steering motor is limited.

The steering control device capable of achieving the above object calculates the reaction force motor, which is the source of the steering reaction force applied to the steering wheel separated from the steering shaft, according to the steering state. It is a steering control device that controls based on the command value. The steering control device includes a first calculation unit that calculates a first axial force acting on the steering shaft based on a current value of a steering motor that is a source of a steering force applied to the steering shaft. , The second calculation unit that calculates the second axial force acting on the steering shaft based on other vehicle state variables different from the current value of the steering motor, the first axial force, and the second. It is provided with a third calculation unit for calculating a third axial force, which is the final axial force to be reflected in the command value based on the axial force of the above. The third calculation unit reduces the degree of reflection of the first axial force on the third axial force when a specific situation in which the current of the steering motor should be limited occurs, while the third calculation unit reduces the degree of reflection of the first axial force on the third axial force. The degree of reflection of the second axial force on the axial force of is increased.

When the current of the steering motor is limited, the first axial force calculated based on the current value of the steering motor, and thus the third axial force reflecting the first axial force may also be limited. .. Therefore, there is a concern that the steering wave force originally required cannot be secured. In this regard, according to the above-mentioned steering control device, when a specific situation occurs in which the current of the steering motor should be limited, the degree of reflection of the first axial force on the third axial force decreases, while the third The degree of reflection of the second axial force on the axial force of is increased. That is, in the third axial force, the second axial force becomes more dominant. The second axial force is less susceptible to the current limitation of the steering motor. Therefore, even when the current of the steering motor is limited, it is possible to secure the steering reaction force as information for the driver.

In the steering control device, the third calculation unit sets a distribution ratio individually set for the first axial force and the second axial force according to the vehicle behavior, the steering state, or the road surface condition. The third axial force may be calculated by adding up the multiplied values. In this case, the third arithmetic unit reduces the distribution ratio of the first axial force to the third axial force when a specific situation occurs in which the current of the steering motor should be limited. The distribution ratio of the second axial force to the third axial force may be increased.

According to this configuration, when a specific situation occurs in which the current of the steering motor should be limited, the distribution ratio of the first axial force to the third axial force is reduced, so that the third axial force is second to the third axial force. The degree of reflection of the axial force of 1 can be reduced. Further, when a specific situation occurs in which the current of the steering motor should be limited, the second axial force with respect to the third axial force is increased by increasing the distribution ratio of the second axial force to the third axial force. The degree of reflection can be increased. Further, by increasing or decreasing the distribution ratio of the first axial force and the distribution ratio of the second axial force, it is possible to switch between the first axial force and the second axial force step by step. Therefore, for example, it is possible to gradually secure the steering reaction force as information for the driver according to the degree of a specific situation in which the current of the steering motor should be limited.

In the steering control device, when a specific situation occurs in which the current of the steering motor should be limited, the distribution ratio of the first axial force to the third axial force is further reduced, while the third. Based on the viewpoint of further increasing the distribution ratio of the second axial force to the axial force of the first axial force, the fourth axial force for individually calculating the distribution ratio for the current limitation to the first axial force and the second axial force. It may have a calculation unit. On the premise of this, the third calculation unit determines the distribution ratio for the current limitation calculated by the fourth calculation unit when a specific situation in which the current of the steering motor should be limited occurs. It may be used to calculate the third axial force.

According to this configuration, when a specific situation occurs in which the current of the steering motor should be limited, the third axial force is calculated using the distribution ratio for current limitation calculated by the fourth calculation unit. By doing so, the distribution ratio of the first axial force to the third axial force can be further reduced, while the distribution ratio of the second axial force to the third axial force can be further increased.

In the steering control device, the fourth calculation unit determines the distribution ratio of the first axial force to the third axial force when a specific situation in which the current of the steering motor should be limited occurs. While setting it to 0%, the distribution ratio of the second axial force to the third axial force may be set to 100%.

According to this configuration, when a specific situation occurs in which the current of the steering motor should be limited, the first axial force calculated based on the current value of the steering motor is not used, and the current value of the steering motor is not used. The second axial force calculated based on other vehicle state variables other than the above is calculated as the third axial force. Therefore, even when the current of the steering motor is limited, it is possible to more appropriately secure the steering reaction force as information for the driver.

In the steering control device, the third calculation unit calculates the first axial force as it is as the third axial force when a specific situation in which the current of the steering motor should be limited does not occur. On the other hand, when a specific situation that should limit the current of the steering motor occurs, the second axial force may be calculated as it is as the third axial force.

According to this configuration, when a specific situation occurs in which the current of the steering motor should be limited, the first axial force calculated based on the current value of the steering motor is not used, and the current value of the steering motor is not used. The second axial force calculated based on other vehicle state variables other than the above is calculated as the third axial force. Therefore, even when the current of the steering motor is limited, it is possible to secure the steering reaction force as information for the driver.

The steering control device may include a steering control unit that controls the steering motor according to the steering state. In this case, the steering control unit sets a value of a flag indicating whether or not a specific situation has occurred in which the current of the steering motor should be limited based on whether or not the predetermined determination condition is satisfied. You may do it. Further, the third calculation unit may recognize that a specific situation has occurred in which the current of the steering motor should be limited based on the value of the flag set by the steering control unit.

According to this configuration, it is not necessary for the third arithmetic unit to determine whether or not a specific situation has occurred in which the current of the steering motor should be limited based on whether or not the predetermined determination condition is satisfied. Therefore, it is possible to reduce the calculation load of the third calculation unit.

According to the steering control device of the present invention, even when the current of the steering motor is limited, it is possible to secure the steering reaction force as information for the driver.

FIG. 3 is a configuration diagram of a steering device of a steer-by-wire system in which the first embodiment of the steering control device is mounted. The block diagram of the control apparatus in 1st Embodiment. The block diagram of the steering reaction force command value calculation unit in 1st Embodiment. The block diagram of the axial force calculation part in 2nd Embodiment. The block diagram of the steering reaction force command value calculation unit in the sixth embodiment. The block diagram of the axial force calculation part in 7th Embodiment.

<First Embodiment>
Hereinafter, a first embodiment in which the steering control device is embodied as a steer-by-wire type steering device will be described.

As shown in FIG. 1, the steering device 10 of the vehicle has a steering shaft 12 connected to the steering wheel 11. Further, the steering device 10 has a steering shaft 14 extending along the vehicle width direction (left-right direction in FIG. 1). The left and right steering wheels 16 and 16 are connected to both ends of the steering shaft 14 via tie rods 15 and 15, respectively. The steering angle θ _w of the steering wheels 16 and 16 is changed by the linear motion of the steering shaft 14. The steering shaft 12 and the steering shaft 14 constitute a steering mechanism of the vehicle.

Further, the steering device 10 has a reaction force motor 31, a deceleration mechanism 32, a rotation angle sensor 33, and a torque sensor 34 as a configuration for generating a steering reaction force. Incidentally, the steering reaction force means a force acting in the direction opposite to the operation direction of the steering wheel 11 by the driver. By applying the steering reaction force to the steering wheel 11, it is possible to give the driver an appropriate feeling of response.

The reaction force motor 31 is a source of steering reaction force. As the reaction force motor 31, for example, a three-phase brushless motor is adopted. The rotation shaft of the reaction force motor 31 is connected to the steering shaft 12 via the reduction mechanism 32. The torque of the reaction force motor 31 is applied to the steering shaft 12 as a steering reaction force.

The rotation angle sensor 33 is provided in the reaction force motor 31. The rotation angle sensor 33 detects the rotation angle θ _a of the reaction force motor 31. The rotation angle θ _a of the reaction force motor 31 is used for calculating the steering angle θ _s . The reaction force motor 31 and the steering shaft 12 are interlocked with each other via the reduction mechanism 32. Therefore, there is a correlation between the rotation angle θ _a of the reaction force motor 31 and the rotation angle of the steering shaft 12, and eventually the steering angle θ _s which is the rotation angle of the steering wheel 11. Therefore, the steering angle θ _s can be obtained based on the rotation angle θ _a of the reaction force motor 31.

The torque sensor 34 detects the steering torque _Th , which is the torque applied to the steering shaft 12 through the rotation operation of the steering wheel 11. The torque sensor 34 detects the steering torque _Th applied to the steering shaft 12 based on the twist amount of the torsion bar provided in the middle of the steering shaft 12. The torque sensor 34 is provided on the steering wheel 11 side of the steering shaft 12 with respect to the reduction mechanism 32.

Further, the steering device 10 has a steering motor 41, a deceleration mechanism 42, and a rotation angle sensor 43 as a configuration for generating a steering force which is a power for steering the steering wheels 16 and 16. There is.

The steering motor 41 is a source of steering force. As the steering motor 41, for example, a three-phase brushless motor is adopted. The rotation shaft of the steering motor 41 is connected to the pinion shaft 44 via the reduction mechanism 42. The pinion teeth 44a of the pinion shaft 44 are meshed with the rack teeth 14b of the steering shaft 14. The torque of the steering motor 41 is applied to the steering shaft 14 as a steering force via the pinion shaft 44. In response to the rotation of the steering motor 41, the steering shaft 14 moves along the vehicle width direction, which is the left-right direction in FIG.

The rotation angle sensor 43 is provided in the steering motor 41. The rotation angle sensor 43 detects the rotation angle θ _b of the steering motor 41.
Incidentally, the steering device 10 has a pinion shaft 13. The pinion shaft 13 is provided so as to intersect with the steering shaft 14. The pinion teeth 13a of the pinion shaft 13 are meshed with the rack teeth 14a of the steering shaft 14. The reason for providing the pinion shaft 13 is to support the steering shaft 14 together with the pinion shaft 44 inside a housing (not shown). That is, the steering shaft 14 is movably supported along the axial direction thereof and is pressed toward the pinion shafts 13 and 44 by a support mechanism (not shown) provided in the steering device 10. As a result, the steering shaft 14 is supported inside the housing. However, another support mechanism for supporting the steering shaft 14 to the housing may be provided without using the pinion shaft 13.

Further, the steering device 10 has a control device 50. The control device 50 controls the reaction force motor 31 and the steering motor 41 based on the detection results of various sensors mounted on the vehicle. As the sensor, in addition to the rotation angle sensor 33, the torque sensor 34, and the rotation angle sensor 43 described above, there is a vehicle speed sensor 501. The vehicle speed sensor 501 detects the vehicle speed V, which is the traveling speed of the vehicle.

The control device 50 executes reaction force control that generates a steering reaction force according to the steering torque _Th through the control of the reaction force motor 31. The control device 50 calculates a target steering reaction force based on the steering torque _Th and the vehicle speed V, and calculates a steering reaction force command value based on the calculated target steering reaction force. The control device 50 supplies the current required for generating the steering reaction force according to the steering reaction force command value to the reaction force motor 31.

The control device 50 executes steering control for steering the steering wheels 16 and 16 according to the steering state through the control of the steering motor 41. The control device 50 calculates the pinion angle θ _p , which is the actual rotation angle of the pinion shaft 44, based on the rotation angle θ _b of the steering motor 41 detected through the rotation angle sensor 43. This pinion angle θ _p is a value that reflects the steering angles θ _w of the steering wheels 16 and 16. Further, the control device 50 calculates the steering angle θ _s based on the rotation angle θ _a of the reaction force motor 31 detected through the rotation angle sensor 33, and the target of the pinion angle θ _p based on the calculated steering angle θ _s . Calculate the target pinion angle, which is a value. Then, the control device 50 obtains a deviation between the target pinion angle and the actual pinion angle θ _p , and controls the power supply to the steering motor 41 so as to eliminate the deviation.

Next, the control device 50 will be described in detail.
As shown in FIG. 2, the control device 50 has a reaction force control unit 50a for executing reaction force control and a steering control unit 50b for executing steering control.

The reaction force control unit 50a has a steering angle calculation unit 51, a steering reaction force command value calculation unit 52, and an energization control unit 53.
The steering angle calculation unit 51 calculates the steering angle θ _s of the steering wheel 11 based on the rotation angle θ _a of the reaction force motor 31 detected through the rotation angle sensor 33.

The steering reaction force command value calculation unit 52 calculates the steering reaction force command value T ^* based on the steering torque _Th and the vehicle speed V. The steering reaction force command value calculation unit 52 calculates a steering reaction force command value T ^* having a larger absolute value as the absolute value of the steering torque _Th is larger and the vehicle speed V is slower. The steering reaction force command value calculation unit 52 will be described in detail later.

The energization control unit 53 supplies electric power corresponding to the steering reaction force command value T ^* to the reaction force motor 31. Specifically, the energization control unit 53 calculates the current command value for the reaction force motor 31 based on the steering reaction force command value T ^* . Further, the energization control unit 53 detects the actual value of the current _Ia generated in the power feeding path through the current sensor 54 provided in the feeding path for the reaction force motor 31. The value of this current I _a is the value of the actual current supplied to the reaction force motor 31. Then, the energization control unit 53 obtains a deviation between the current command value and the actual current _Ia value, and controls the power supply to the reaction force motor 31 so as to eliminate the deviation. As a result, the reaction force motor 31 generates torque according to the steering reaction force command value T ^* . It is possible to give the driver an appropriate feeling of response according to the road surface reaction force.

The steering control unit 50b has a pinion angle calculation unit 61, a target pinion angle calculation unit 62, a pinion angle feedback control unit 63, a limitation control unit 64, and an energization control unit 65.
The pinion angle calculation unit 61 calculates the pinion angle θ _p , which is the actual rotation angle of the pinion shaft 44, based on the rotation angle θ _b of the steering motor 41 detected through the rotation angle sensor 43. The steering motor 41 and the pinion shaft 44 are interlocked with each other via the reduction mechanism 42. Therefore, there is a correlation between the rotation angle θ _b of the steering motor 41 and the pinion angle θ _p . Using this correlation, the pinion angle θ _p can be obtained from the rotation angle θ _b of the steering motor 41. Further, the pinion shaft 44 is meshed with the steering shaft 14. Therefore, there is also a correlation between the pinion angle θ _p and the amount of movement of the steering shaft 14. That is, the pinion angle θ _p is a value that reflects the steering angles θ _w of the steering wheels 16 and 16.

The target pinion angle calculation unit 62 calculates the target pinion angle θ _p ^* based on the steering angle θ _s calculated by the steering angle calculation unit 51 and the vehicle speed V detected through the vehicle speed sensor 501. The target pinion angle calculation unit 62 sets a steering angle ratio, which is the ratio of the steering angle θ _w to the steering angle θ _s , according to, for example, the vehicle speed V, and the target pinion angle θ _p according to the set steering angle ratio. ^* Is calculated. In the target pinion angle calculation unit 62, the steering angle θ _w with respect to the steering angle θ _s becomes larger as the vehicle speed V becomes slower, and the steering angle θ _w with respect to the steering angle θ _s becomes smaller as the vehicle speed V becomes faster. The target pinion angle θ _p ^* is calculated as described above.

Incidentally, depending on the product specifications and the like, the target pinion angle calculation unit 62 may set the target pinion angle θ _p ^* to the same value as the steering angle θ _s . In this case, the steering angle ratio, which is the ratio of the steering angle θ _s to the steering angle θ _w , is “1: 1”.

The pinion angle feedback control unit 63 captures the target pinion angle θ _p ^* calculated by the target pinion angle calculation unit 62 and the actual pinion angle θ _p calculated by the pinion angle calculation unit 61. The pinion angle feedback control unit 63 calculates the pinion angle command value T _p ^* through the feedback control of the pinion angle θ _p so that the actual pinion angle θ _p follows the target pinion angle θ _p ^* .

The limit control unit 64 calculates a limit value _Ilim for limiting the amount of current supplied to the steering motor 41, for example, according to the heat generation state of the steering motor 41. The limit value _Ilim is set as an upper limit value of the amount of current supplied to the steering motor 41 from the viewpoint of protecting the steering motor 41 from overheating. The limit control unit 64 sets the limit value _Ilim based on the comparison result between the temperature _Tm of the steering motor 41 and the temperature threshold value detected through the temperature sensor 62a provided in the vicinity of the feeding path for the steering motor 41. Calculate.

In the limiting control unit 64, when the temperature _Tm of the steering motor 41 does not exceed the temperature threshold value, the energization control unit 65 rotates based on the maximum current value that can be applied without overheating the steering motor 41. The limit value _Ilim having a large absolute value that does not limit the current to be supplied to the rudder motor 41 is calculated. On the other hand, the limiting control unit 64 has an absolute value smaller than the maximum current value that can be applied without overheating of the steering motor 41 when the temperature _Tm of the steering motor 41 exceeds the temperature threshold value. Calculate the limit value _Ilim . The limit control unit 64 calculates a limit value _Ilim having an absolute value smaller as the temperature T _m of the steering motor 41 is higher.

Incidentally, the limit value _Ilim may be a fixed value which is a fixed value. The limit value _Ilim , which is a fixed value, is stored in the storage device of the control device 50. When this configuration is adopted, the limiting control unit 64 limits the current amount of the steering motor 41 when the temperature T _m of the steering motor 41 exceeds the temperature threshold, regardless of the temperature T _m of the steering motor 41. The limit value I _lim , which is a fixed value, may be set as the value I _lim . Further, the limit control unit 64 may not set the limit value _Ilim for the current amount of the steering motor 41 when the temperature T _m of the steering motor 41 does not exceed the temperature threshold value.

The limit control unit 64 sets the value of the flag F based on whether the temperature T _m of the steering motor 41 exceeds the temperature threshold value, that is, whether the current amount of the steering motor 41 should be limited. do. The limit control unit 64 sets the value of the flag F to "1" when the temperature T _m of the steering motor 41 exceeds the temperature threshold value, that is, when the current amount of the steering motor 41 should be limited. Set to. The limit control unit 64 sets the value of the flag F to "0" when the temperature T _m of the steering motor 41 does not exceed the temperature threshold value, that is, when the current amount of the steering motor 41 should not be limited. Set to.

The energization control unit 65 supplies electric power according to the pinion angle command value T _p ^* to the steering motor 41. Specifically, the energization control unit 65 calculates the current command value for the steering motor 41 based on the pinion angle command value T _p ^* . Further, the energization control unit 65 detects the value of the actual current _Ib generated in the feeding path through the current sensor 66 provided in the feeding path for the steering motor 41. The value of this current I _b is the value of the actual current supplied to the steering motor 41. Then, the energization control unit 65 obtains a deviation between the current command value and the actual current I _b value, and controls the feeding to the steering motor 41 so as to eliminate the deviation (feedback control of the current I _b ). As a result, the steering motor 41 rotates by an angle corresponding to the pinion angle command value T _p ^* .

When the limit value _Ilim is calculated by the limit control unit 64, the energization control unit 65 limits the amount of current supplied to the steering motor 41 according to the limit value _Ilim . The energization control unit 65 compares the absolute value of the current to be supplied to the steering motor 41 with the limit value _Ilim . When the absolute value of the current to be supplied to the steering motor 41 is larger than the limit value I _lim , the energization control unit 65 limits the absolute value of the current supplied to the steering motor 41 to the limit value I _lim . As a result, the torque generated by the steering motor 41 is limited to the torque corresponding to the limit value _Ilim . On the other hand, when the absolute value of the current to be supplied to the steering motor 41 is equal to or less than the limit value I _lim , the energization control unit 65 steers the original current calculated through the feedback control of the current I _b as it is. It is supplied to the motor 41. The torque generated by the steering motor 41 is not limited.

Next, the steering reaction force command value calculation unit 52 will be described in detail.
As shown in FIG. 3, the steering reaction force command value calculation unit 52 includes a target steering reaction force calculation unit 71, an axial force calculation unit 72, and a subtractor 73.

The target steering reaction force calculation unit 71 calculates the target steering reaction force T1 ^* based on the steering torque _Th and the vehicle speed V. The target steering reaction force T1 ^* is a target value of the torque acting in the direction opposite to the operating direction of the steering wheel 11 to be generated through the reaction force motor 31. The target steering reaction force calculation unit 71 calculates the target steering reaction force _T1 ^* having a larger absolute value as the absolute value of the steering torque Th is larger and the vehicle speed V is slower.

The axial force calculation unit 72 calculates the axial force acting on the steering shaft 14 based on the pinion angle θ _p , the value of the current I _b of the steering motor 41, and the vehicle speed V, and the calculated axial force is calculated by the steering wheel. The torque conversion value T2 ^* is calculated by converting the torque to 11 or the steering shaft 12. The axial force calculation unit 72 will be described in detail later.

The subtractor 73 subtracts the torque conversion value T2 ^* calculated by the axial force calculation unit 72 from the target steering reaction force T1 ^* calculated by the target steering reaction force calculation unit 71, so that the steering reaction force command value T ^* Is calculated.

Next, the axial force calculation unit 72 will be described in detail.
As shown in FIG. 3, the axial force calculation unit 72 includes an angle axial force calculation unit 81A, a current axial force calculation unit 81B, an axial force distribution calculation unit 81C, and a converter 81D.

The angle axial force calculation unit 81A calculates the angle axial force AF ₁ , which is an ideal value of the axial force acting on the steering shaft 14, based on the pinion angle θ _p . The angle axis force calculation unit 81A calculates the angle axis force AF ₁ using, for example, the angle axis force map stored in the storage device of the control device 50. The angle axis force map is a map in which the horizontal axis is the pinion angle θ _p and the vertical axis is the angle axis force AF ₁ , and the relationship between the pinion angle θ _p and the angle axis force AF ₁ is defined according to the vehicle speed V. .. The angular axial force map has the following characteristics. That is, the angle axial force AF ₁ is set to a larger absolute value as the absolute value of the pinion angle θ _p increases and the vehicle speed V becomes slower. The absolute value of the angular axial force AF ₁ increases linearly with respect to the increase in the absolute value of the pinion angle θ _p . The angular axial force AF ₁ is set to have the same sign as the sign of the pinion angle θ _p . The angular axial force AF ₁ is an axial force that does not reflect the force acting on the road surface condition or the steering shaft 14.

The current axial force calculation unit 81B calculates the current axial force AF ₂ acting on the steering shaft 14 based on the value of the current I _b of the steering motor 41. Here, the values of the current I _b of the steering motor 41 are the target pinion angle θ _p ^* and the actual pinion due to the fact that the disturbance corresponding to the road surface condition such as the road surface friction resistance acts on the steering wheels 16 and 16. It changes depending on the difference generated between the angle θ _p and the angle θ p. That is, the value of the current I _b of the steering motor 41 reflects the actual road surface condition acting on the steering wheels 16 and 16. Therefore, it is possible to calculate the axial force reflecting the influence of the road surface condition based on the value of the current I _b of the steering motor 41. The current axial force AF ₂ is obtained, for example, by multiplying the gain, which is a coefficient corresponding to the vehicle speed V, by the value of the current I _b of the steering motor 41. The current axial force AF ₂ is an axial force that reflects the force acting on the steering shaft 14 in the road surface condition or via the steering wheels 16 and 16.

The axial force distribution calculation unit 81C individually sets the distribution ratio for the angular axial force AF ₁ and the distribution ratio for the current axial force AF ₂ according to various vehicle state variables. The vehicle state variable is a variable that reflects the state of the vehicle including the vehicle behavior, the steering state, or the road surface state, and is, for example, yaw rate, lateral acceleration, steering angle θ _s , pinion angle θ _p , vehicle speed V, steering speed, and the like. And pinion angular velocity and the like. The steering speed is obtained by differentiating the steering angle θ _s . The pinion angular velocity is obtained by differentiating the pinion angle θ _p .

The axial force distribution calculation unit 81C reflects the steering reaction force command value T ^* by adding up the values obtained by multiplying the angular axial force AF ₁ and the current axial force AF ₂ by the distribution ratios individually set. The final axial force AF ₃ which is the final axial force is calculated. The final axial force AF ₃ is expressed by the following equation (1).

AF ₃ = AF ₁・ DR ₁ + AF ₂・ DR ₂ … (1)
However, "DR ₁ " is the distribution ratio to the angle axial force AF ₁ , and "DR ₂ " is the distribution ratio to the current axial force AF ₂ . The distribution ratio DR ₁ indicates the degree to which the angular axial force AF ₁ is reflected in the final axial force AF ₃ . The distribution ratio DR ₂ indicates the degree to which the current axial force AF ₂ is reflected in the final axial force AF ₃ .

The axial force distribution calculation unit 81C sets the values of the two distribution ratios DR ₁ and DR ₂ , respectively, based on various vehicle state variables that reflect the running state or steering state of the vehicle. Further, the axial force distribution calculation unit 81C sets the values of the two distribution ratios DR ₁ and DR ₂ in the range of "0 (0%)" to "1 (100%)" based on the product specifications and the like, for example, "0". It is possible to set in increments of "1.1". However, the axial force distribution calculation unit 81C sets the values of the two distribution ratios DR ₁ and DR ₂ , respectively, so that the total of the values of the two distribution ratios DR ₁ and DR ₂ is “1”.

The converter 81D calculates the torque conversion value T2 ^* by converting the final axial force AF ₃ calculated by the axial force distribution calculation unit 81C into the torque for the steering wheel 11.
According to the steering device 10 configured in this way, the torque conversion value T2 ^* obtained by converting the final axial force AF ₃ calculated by the axial force calculation unit 72 into torque is reflected in the steering reaction force command value T ^* . , It is possible to apply a steering reaction force to the steering wheel 11 according to the vehicle behavior or the road surface condition. Therefore, the driver can grasp the vehicle behavior or the road surface condition by feeling the steering reaction force via the steering wheel 11 as a response.

However, in the steering device 10, there are concerns about the following. That is, when the current amount of the steering motor 41 is limited through the execution of the overheat protection function of the steering motor 41, the current axial force AF ₂ and eventually the steering motor 41 are caused by the limitation of the current amount. The generated torque may decrease. Therefore, for example, there is a concern that the steering reaction force originally required cannot be secured even though the steering reaction force should be further increased as information for the driver.

Therefore, the following configuration is adopted as the axial force calculation unit 72.
As shown in FIG. 3, the axial force calculation unit 72 has a distribution ratio calculation unit 81E. The distribution ratio calculation unit 81E takes in the value of the flag F set by the limit control unit 64. When the value of the flag F is "1", the distribution ratio calculation unit 81E sets the values of the distribution ratios DR ₁ and DR ₂ for the current limitation of the steering motor 41. The distribution ratios DR ₁ and DR ₂ for current limitation are used in preference to the distribution ratios DR ₁ and DR ₂ calculated by the axial force distribution calculation unit 81C.

The distribution ratio calculation unit 81E is the distribution ratio of the angular axial force AF ₁ to the final axial force AF ₃ when the value of the flag F is “1”, that is, when the current amount of the steering motor 41 should be limited. The value of DR ₁ is set to "1 (100%)", while the value of the distribution ratio DR ₂ of the current axial force AF ₂ to the final axial force AF ₃ is set to "0 (0%)". Further, the distribution ratio calculation unit 81E has distribution ratios DR ₁ and DR ₂ for when the value of the flag F is "0", that is, when the current amount of the steering motor 41 should not be limited. Do not set.

When the distribution ratios DR ₁ and DR ₂ for current limitation are set by the distribution ratio calculation unit 81C, the axial force distribution calculation unit 81C calculates the distribution ratios DR ₁ and DR ₂ to be set by itself. It is used in preference to DR ₁ and DR ₂ . Here, the value of the distribution ratio DR ₁ for the current limiting of the angular axial force AF ₁ is set to "1 (100%)", while the distribution ratio DR ₂ for the current limiting of the current axial force AF ₂ is set. The value is set to "0 (0%)". Therefore, as can be seen from the above equation (1), the value of the final axial force AF ₃ is the same as the value of the angular axial force AF ₁ calculated by the angle axial force calculation unit 81A. That is, the angle axial force AF ₁ calculated by the angle axial force calculation unit 81A is used as it is as the final axial force AF ₃ for controlling the reaction force motor 31.

Incidentally, depending on the product specifications and the like, the axial force distribution calculation unit 81C may have the function of the distribution ratio calculation unit 81E. In this case, it is possible to adopt a configuration in which the distribution ratio calculation unit 81E is omitted as the axial force calculation unit 72. The axial force distribution calculation unit 81C takes in the value of the flag F set by the limitation control unit 64. When the value of the flag F is "1", the axial force distribution calculation unit 81C sets the values of the distribution ratios DR ₁ and DR ₂ for the current limitation of the steering motor 41. The distribution ratios DR ₁ and DR ₂ for current limitation have priority over the distribution ratios DR ₁ and DR ₂ calculated according to various vehicle state variables that reflect the vehicle behavior, steering condition, or road surface condition. used.

Next, the operation of the first embodiment will be described.
In normal times, when the current of the steering motor 41 is not limited, the control device 50 adds up the angular axial force AF ₁ and the current axial force AF ₂ at a distribution ratio set according to the vehicle behavior, steering condition, or road surface condition. The final axial force AF ₃ is calculated by the above, and the reaction force motor 31 is controlled by using the calculated final axial force AF ₃ . The angular axial force AF ₁ is an ideal axial force based on the pinion angle θ _p and is an axial force that does not reflect the road surface condition. The current axial force AF ₂ is an axial force based on the value of the current I _b of the steering motor 41 and is an axial force that reflects the road surface condition. Therefore, the reaction force motor 31 generates a steering reaction force according to the vehicle behavior, the steering state, or the road surface state. Therefore, the driver can grasp the vehicle behavior, the steering state, or the road surface state by feeling the steering reaction force via the steering wheel 11 as a response.

Next, when the current of the steering motor 41 is limited based on the viewpoint of overheat protection of the steering motor 41, the control device 50 uses the limiting value _Ilim set by the limiting control unit 64 to steer the motor. The amount of current supplied to 41 is limited. By limiting the value of the current I _b of the steering motor 41 to at least the limit value _Ilim , the temperature rise of the steering motor 41 is suppressed, and the current I _b of the steering motor 41 decreases. The temperature of the rudder motor 41 gradually decreases, and eventually reaches a temperature below the temperature threshold. As a result, the steering motor 41 is protected from overheating.

Further, when the current of the steering motor 41 is limited from the viewpoint of overheat protection of the steering motor 41, the control device 50 uses the steering motor 41 among the angular axial force AF ₁ and the current axial force AF ₂ . Only the angular axial force AF ₁ that is not affected by the change in the current I _b is reflected in the steering reaction force command value T ^* . Specifically, the control device 50 sets the distribution ratio DR ₁ of the angle axial force AF ₁ to the final axial force AF ₃ to "1 (100%)", while the current axial force AF ₂ to the final axial force AF ₃ The distribution ratio DR ₂ of is set to "0 (0%)". Since the current axial force AF ₂ affected by the change in the current I _b of the steering motor 41 is not reflected in the steering reaction force command value T ^* , the torque generated by the reaction force motor 31 is also the torque generated by the steering motor 41 _. Not affected by change. Therefore, the steering reaction force applied to the steering wheel 11 is not limited due to the limitation of the current _Ib of the steering motor 41.

Even when the current I _b of the steering motor 41 is limited, of the angular axial force AF ₁ and the current axial force AF ₂ , only the angular axial force AF ₁ corresponding to the pinion angle θ _p is the steering reaction force command value. By being reflected in T ^* , a steering reaction force corresponding to the pinion angle θ _p is applied to the steering wheel 11. For example, the angular axial force AF ₁ is set to a larger absolute value as the absolute value of the pinion angle θ _p increases. Therefore, in a situation where the steering reaction force should be increased as information for the driver, for example, when the steering wheel 11 is steered more greatly, an appropriate steering reaction force according to the pinion angle θ _p as information for the driver. Is given to the steering wheel 11.

Therefore, according to the first embodiment, the following effects can be obtained.
(1) When a specific situation occurs in which the current I _b of the steering motor 41 should be limited, the current axial force AF ₂ calculated based on the current I _b of the steering motor 41 is not used, and the steering motor 41 is not used. The angular axial force AF ₁ which is not affected by the current limitation of is calculated as the final axial force AF ₃ which is the final axial force reflected in the steering reaction force command value T ^* . Therefore, even when the current of the steering motor 41 is limited, it is possible to secure the steering reaction force as information for the driver. Further, the steering feel during normal operation of the system in which the current I _b of the steering motor 41 is not limited and the steering feel during the protective operation of the system in which the current I _b of the steering motor 41 is limited are realized at the same time. be able to.

(2) The distribution ratio calculation unit 81E sets the distribution ratio of the current axial force AF ₂ to the final axial force AF ₃ to 0% when a specific situation occurs in which the current _Ib of the steering motor 41 should be limited. On the other hand, the distribution ratio of the angular axial force AF ₁ to the final axial force AF ₃ is set to 100%. Therefore, when a specific situation occurs in which the current _Ib of the steering motor 41 should be limited, the distribution ratios DR ₁ and DR ₂ for current limitation calculated by the distribution ratio calculation unit 81E are used for the final shaft. By calculating the force AF ₃ , the steering reaction force as information for the driver can be secured even when the current of the steering motor 41 is limited.

<Second embodiment>
Next, a second embodiment in which the steering control device is embodied in a steer-by-wire type steering device will be described. This embodiment basically has the same configuration as the first embodiment shown in FIGS. 1 and 2 above. This embodiment is different from the first embodiment in that the axial force calculation unit 72 is configured.

As shown in FIG. 4, the axial force calculation unit 72 includes an angle axial force calculation unit 81A, a current axial force calculation unit 81B, a converter 81D, and a switch 81F.
The switch 81F takes in the angle axis force AF ₁ calculated by the angle axis force calculation unit 81A and the current axis force AF ₂ calculated by the current axis force calculation unit 81B as data inputs. Further, the switch 81F takes in the value of the flag F set by the limitation control unit 64 as a control input. The switch 81F has either one of the angle axis force AF ₁ calculated by the angle axis force calculation unit 81A and the current axis force AF ₂ calculated by the current axis force calculation unit 81B based on the value of the flag F. It is selected as the final axial force AF ₃ , which is the final axial force used to control the reaction force motor 31.

When the value of the flag F is "0", the switch 81F selects the current axial force AF ₂ calculated by the current axial force calculation unit 81B as the final axial force AF ₃ . When the value of the flag F is "1", the switch 81F selects the angle axial force AF ₁ calculated by the angular axial force calculation unit 81A as the final axial force AF ₃ .

Next, the operation of the second embodiment will be described.
In the normal state where the current of the steering motor 41 is not limited, the control device 50 uses the current axial force AF ₂ based on the current I _b of the steering motor 41 among the angular axial force AF ₁ and the current axial force AF ₂ as the final axis. It is selected as the force AF ₃ and the selected final axial force AF ₃ is used to control the reaction force motor 31. The current axial force AF ₂ is an axial force based on the current I _b of the steering motor 41 and is an axial force that reflects the road surface condition. Therefore, the reaction force motor 31 generates a steering reaction force according to the vehicle behavior or the road surface condition. Therefore, the driver can grasp the vehicle behavior or the road surface condition by feeling the steering reaction force via the steering wheel 11 as a response.

Further, when the current of the steering motor 41 is limited from the viewpoint of overheat protection of the steering motor 41, the control device 50 uses the steering motor 41 among the angular axial force AF ₁ and the current axial force AF ₂ . The angular axial force AF ₁ that is not affected by the change in the current I _b is selected as the final axial force AF ₃ . Since the current axial force AF ₂ affected by the change in the current I _b of the steering motor 41 is not reflected in the steering reaction force command value T ^* , the torque generated by the reaction force motor 31 is also the torque generated by the steering motor 41 _. Not affected by change. Therefore, the steering reaction force applied to the steering wheel 11 is not limited due to the limitation of the current _Ib of the steering motor 41. Even when the current I _b of the steering motor 41 is limited, an appropriate steering reaction force corresponding to the pinion angle θ _p is applied to the steering wheel 11 as information to the driver.

Therefore, according to the second embodiment, the following effects can be obtained in addition to the same effects as in (1) of the first embodiment.
(3) When the current I _b of the steering motor 41 is limited, the axial force reflected in the steering reaction force command value T ^* is switched from the current axial force AF ₂ to the angular axial force AF ₁ simply by switching the switch 81F. be able to. Therefore, it is possible to reduce the calculation load of the control device 50.

<Third embodiment>
Next, a third embodiment in which the steering control device is embodied in a steer-by-wire type steering device will be described. This embodiment basically has the same configuration as the first embodiment shown in FIGS. 1 to 3 above. The present embodiment may be applied to the second embodiment.

In the first embodiment, as a situation in which the current of the steering motor 41 should be limited, a situation in which the steering motor 41 approaches an overheated state is given as an example, but a situation in which the power supply voltage of the vehicle is lowered is included. You may.

The limiting control unit 64 limits the amount of current supplied to the steering motor 41 according to the voltage Vb of a DC power source such as a battery detected through the voltage sensor 502 shown by the two-dot chain line in _FIG . 2, for example. Calculate the limit value _Ilim of. The limit value _Ilim is set as an upper limit value of the amount of current supplied to the steering motor 41 from the viewpoint of suppressing a decrease in the voltage V _b of the DC power supply. When the voltage V _b of the DC power supply detected through the voltage sensor 502 is equal to or less than the voltage threshold value, the limit control unit 64 calculates the limit value _Ilim according to the voltage value at that time. The voltage threshold value is set with reference to the lower limit value of the guaranteed operation voltage range in which the operation of the steering motor 41 is guaranteed.

Further, the limiting control unit 64 sets the value of the flag F based on whether the voltage V _b of the DC power supply is equal to or less than the voltage threshold value, that is, whether the voltage V _b of the DC power supply is lowered. The limiting control unit 64 sets the value of the flag F to "1" when the voltage V _b of the DC power supply is equal to or less than the voltage threshold value, that is, when the voltage V _b of the DC power supply is low. The limiting control unit 64 sets the value of the flag F to "0" when the voltage V _b of the DC power supply is not equal to or less than the voltage threshold value, that is, when the voltage V _b of the DC power supply is not lowered.

Therefore, according to the third embodiment, the following effects can be obtained.
(4) When the power supply voltage of the vehicle drops, by limiting the current _Ib supplied to the steering motor 41, it is possible to suppress a further drop in the power supply voltage. Further, even if the current _Ib of the steering motor 41 is limited due to the decrease in the power supply voltage of the vehicle, the steering motor 41 is rotated by using the angular axial force AF ₁ which is not affected by the current limitation of the steering motor 41. By controlling the drive of the rudder motor 41, it is possible to apply an appropriate steering reaction force as information to the driver.

<Fourth Embodiment>
Next, a fourth embodiment in which the steering control device is embodied in a steer-by-wire type steering device will be described. This embodiment basically has the same configuration as the first embodiment shown in FIGS. 1 to 3 above.

In the first embodiment, when a situation occurs in which the current I _b of the steering motor 41 should be limited, the distribution ratio calculation unit 81E sets the distribution ratio DR ₁ of the angular axial force AF ₁ to “1 (100%)). On the other hand, the distribution ratio DR ₂ of the current axial force AF ₂ is set to "0 (0%)", but the present invention is not limited to this.

For example, when a situation occurs in which the current I _b of the steering motor 41 should be limited, the distribution ratio DR ₁ of the angular axial force AF ₁ is expressed by the following relational expression (2) or relational expression (3). And the value of the distribution ratio DR ₂ of the current axial force AF ₂ may be set. However, the two distribution ratios DR ₁ : DR ₂ are set so that the total of them is "1 (100%)". Further, the two distribution ratios DR ₁ and DR ₂ are set to appropriate values depending on the product specifications and the like.

DR ₁ : DR ₂ = 0.8 (80%): 0.2 (20%) ... (2)
DR ₁ : DR ₂ = 0.9 (90%): 0.1 (10%) ... (3)
As described above, the value of the distribution ratio DR ₁ of the angular axial force AF ₁ does not necessarily have to be “1 (100%)”. In the two distribution ratios DR ₁ and DR ₂ , when a specific situation occurs in which the current Ib of the steering motor 41 should be limited, the degree of reflection of the current axial force AF ₂ on the final axial force AF ₃ decreases, while the final degree of reflection is reduced. The value may be set so that the degree of reflection of the angular axial force AF ₁ with respect to the axial force AF ₃ increases. That is, it is sufficient that the angular axial force AF ₁ becomes more dominant in the final axial force AF ₃ .

Therefore, according to the fourth embodiment, the following effects can be obtained.
(5) When a specific situation occurs in which the current _Ib of the steering motor 41 should be limited, the degree of reflection of the current axial force AF ₂ on the final axial force AF ₃ decreases, while the angle axis with respect to the final axial force AF ₃ The degree of reflection of force AF ₁ increases. That is, since the angular axial force AF ₁ becomes more dominant in the final axial force AF ₃ , the steering reaction force as information for the driver is secured even when the current _Ib of the steering motor 41 is limited. can do.

<Fifth Embodiment>
Next, a fifth embodiment in which the steering control device is embodied in a steer-by-wire type steering device will be described. This embodiment basically has the same configuration as the first embodiment shown in FIGS. 1 to 3 above.

Similar to the third embodiment above, when a plurality of situations are assumed as situations in which the current of the steering motor 41 should be limited, the values of the two distribution ratios DR ₁ and DR ₂ are assumed according to those situations. May be different. The specific configuration is as follows.

In addition to setting the value of the flag F, the limit control unit 64 generates identification information unique to each situation in which the current of the steering motor 41 should be limited.
The distribution ratio calculation unit 81E takes in the value of the flag F and the identification information. When the value of the flag F is "1", the distribution ratio calculation unit 81E has an angular axial force with respect to the final axial force AF ₃ according to the identification information, that is, according to the situation in which the current of the steering motor 41 should be limited. The value of the distribution ratio DR ₁ of AF ₁ and the value of the distribution ratio DR ₂ of the current axial force AF ₂ with respect to the final axial force AF ₃ are set. At this time, the value of the distribution ratio DR ₁ of the angular axial force AF ₁ and the value of the distribution ratio DR ₂ of the current axial force AF ₂ are set to different values depending on the situation in which the current of the steering motor 41 should be limited. .. However, the two distribution ratios DR ₁ and DR ₂ are set so that the total of them is "1 (100%)". Further, the two distribution ratios DR ₁ and DR ₂ are set to appropriate values depending on the product specifications and the like.

For example, when the steering motor 41 is in an overheated state, the value of the distribution ratio DR ₁ of the angular axial force AF ₁ and the distribution ratio DR ₂ of the current axial force AF ₂ are expressed by the following relational expression (4). Set the value.

DR ₁ : DR ₂ = 1 (100%): 0 (0%) ... (4)
Further, when the voltage V _b of the DC power supply drops, the value of the distribution ratio DR ₁ of the angular axial force AF ₁ and the current axial force AF are expressed by the following relational expression (5) or (6). Set the value of the distribution ratio DR ₂ of ₂ .

DR ₁ : DR ₂ = 0.8 (80%): 0.2 (20%) ... (5)
DR ₁ : DR ₂ = 0.9 (90%): 0.1 (10%) ... (6)
Therefore, according to the fifth embodiment, the following effects can be obtained.

(6) When a specific situation occurs in which the current I _b of the steering motor 41 should be limited, the distribution ratios of the two distribution ratios DR ₁ and DR ₂ are set according to the situation in which the current I _b of the steering motor 41 should be limited. The value is set. However, regardless of the situation in which the current I _b of the steering motor 41 should be limited, the angular axial force AF ₁ becomes more dominant in the final axial force AF ₃ . Therefore, when a specific situation occurs in which the current I _b of the steering motor 41 should be limited, the steering reaction force as information to the driver is applied according to the situation in which the current I _b of the steering motor 41 should be limited. Can be secured.

<Sixth Embodiment>
Next, a sixth embodiment in which the steering control device is embodied in a steer-by-wire type steering device will be described. This embodiment basically has the same configuration as the first embodiment shown in FIGS. 1 to 3 above. The present embodiment may be applied to the third to fifth embodiments.

Depending on the product specifications, the following configuration may be adopted as the axial force calculation unit 72. That is, as shown in FIG. 5, the axial force calculation unit 72 is added to the angle axial force calculation unit 81A, the current axial force calculation unit 81B, the axial force distribution calculation unit 81C, the converter 81D, and the distribution ratio calculation unit 81E. It has a lateral G-axis force calculation unit 81G.

The lateral G-force calculation unit 81G calculates the lateral G-force AF ₄ which is the axial force acting on the steering shaft 14 based on the lateral acceleration LA detected through the lateral acceleration sensor 503 provided in the vehicle. The lateral G-force AF ₄ is obtained, for example, by multiplying the lateral acceleration LA by a gain which is a coefficient corresponding to the vehicle speed V. Since the behavior of the vehicle is reflected in the lateral acceleration LA, the behavior of the vehicle is also reflected in the lateral G-force AF ₄ calculated based on the lateral acceleration LA. Since the lateral G-force AF ₄ is calculated based on the lateral acceleration LA, it is not easily affected by the change in the current I _b of the steering motor 41.

The axial force distribution calculation unit 81C sets the angular axial force AF ₁ , the current axial force AF ₂ , and the lateral G axial force AF ₄ according to various vehicle state variables that reflect the running state or steering state of the vehicle. The final axial force AF ₃ is calculated by adding up the distribution ratios of. Examples of vehicle state variables include vehicle speed V, steering angle θ _s , and pinion angle θ _p . By reflecting this final axial force AF ₃ in the steering reaction force command value T ^* , it becomes possible to apply a more appropriate steering reaction force according to the vehicle behavior to the steering wheel 11. Incidentally, the final axial force AF ₃ at this time is expressed by the following equation (7).

AF ₃ = AF ₁・ DR ₁ ＋ AF ₂・ DR ₂ ＋ AF ₄・ DR ₄ … (7)
However, "DR ₁ " is the distribution ratio to the angular axial force AF ₁ , "DR ₂ " is the distribution ratio to the current axial force AF ₂ , and "DR ₄ " is the distribution ratio to the lateral G-force AF ₄ .

When the value of the flag F is "1", the distribution ratio calculation unit 81E has distribution ratios DR ₁ and DR ₂ for current limitation with respect to the angle axial force AF ₁ , the current axial force AF ₂ and the lateral G axial force AF ₄ . , Set the value of DR ₄ . These distribution ratios DR ₁ , DR ₂ , and DR ₄ for current limitation correspond to the product specifications, etc. from the viewpoint of suppressing the influence of the steering reaction force command value T ^* and the current limitation of the steering motor 41 on the steering reaction force. Is set to an appropriate value. Further, the distribution ratios DR _{1, DR 2, and DR 4 for current limitation are used in preference to the distribution ratios DR 1 , DR 2 , and DR 4 set by the} axial force distribution calculation unit 81C.

When the value of the flag F is "1", the distribution ratio calculation unit 81E reduces the degree of reflection of the current axial force AF ₂ on the final axial force AF ₃ , while the angular axial force AF ₁ and the angle axial force AF 1 with respect to the final axial force AF ₃ . Set the values of the distribution ratios DR ₁ , DR ₂ , and DR ₄ for the current limitation so that the degree of reflection of the lateral G-force AF ₄ as a total increases.

When the value of the flag F is "1", the distribution ratio calculation unit 81E sets the value of the distribution ratio DR ₂ of the current axial force AF ₂ to "0 (0%)" and the distribution ratio DR of the angle axial force AF ₁ for example. The value of ₁ may be set to "0.5 (50%)", and the value of the distribution ratio DR ₄ of the lateral G-force AF ₄ may be set to "0.5 (50%)". Further, when the value of the flag F is "1", the distribution ratio calculation unit 81E sets, for example, the value of the distribution ratio DR ₂ of the current axial force AF ₂ and the value of the distribution ratio DR ₁ of the angular axial force AF ₁ , respectively. While setting it to "0", the value of the distribution ratio DR ₄ of the lateral G-force AF ₄ may be set to "1".

By doing so, the degree of reflection of the current axial force AF ₂ on the final axial force AF ₃ decreases, while the degree of reflection of the angular axial force AF ₁ and the lateral G axial force AF ₄ on the final axial force AF ₃ as a total. To increase. Therefore, the influence of the current limit of the steering motor 41 on the steering reaction force command value T ^* and, by extension, the steering reaction force is suppressed.

Further, as in the fourth embodiment, the distribution ratio calculation unit 81E sets the value of the distribution ratio DR ₂ to the current axial force AF ₂ to "0" even when the value of the flag F is "1". It is not necessary to set it to (0%). When the value of the flag F is "1", the distribution ratio calculation unit 81E sets the value of the distribution ratio DR ₂ of the current axial force AF ₂ to "0.1 (10%)" and distributes the angular axial force AF ₁ . The value of the ratio DR ₁ may be set to "0.6 (60%)", and the value of the distribution ratio DR ₄ of the lateral G-force AF ₄ may be set to "0.3 (30%)".

Even in this way, the degree of reflection of the current axial force AF ₂ on the final axial force AF ₃ decreases, while the degree of reflection of the angular axial force AF ₁ and the lateral G axial force AF ₄ on the final axial force AF ₃ as a whole decreases. To increase. Therefore, the influence of the current limit of the steering motor 41 on the steering reaction force command value T ^* and, by extension, the steering reaction force is suppressed.

Therefore, according to the sixth embodiment, the following effects can be obtained.
(7) Degree of reflection of the current axial force AF ₂ calculated based on the current I _b of the steering motor 41 on the final axial force AF ₃ when a specific situation occurs in which the current I _b of the steering motor 41 should be limited. On the other hand, the degree of reflection of the angular axial force AF ₁ and the lateral G axial force AF ₄ that are not easily affected by the change in the current _Ib of the steering motor 41 on the final axial force AF ₃ as a total increases. Therefore, it is possible to prevent the current limit of the steering motor 41 from affecting the steering reaction force command value T ^* and, by extension, the steering reaction force. Therefore, even when the current _Ib of the steering motor 41 is limited, the steering reaction force as information for the driver can be secured.

(8) Incidentally, as shown in FIG. 5 with reference numerals in parentheses, a yaw rate axial force calculation unit 81H may be provided instead of the lateral G axial force calculation unit 81G. The yaw rate axial force calculation unit 81H calculates the yaw rate axial force AF ₅ which is the axial force acting on the steering shaft 14 based on the yaw rate YR detected through the yaw rate sensor 504 provided in the vehicle. The yaw rate axial force AF ₅ is obtained by multiplying the yaw rate differential value, which is a value obtained by differentiating the yaw rate YR, by the vehicle speed gain, which is a coefficient corresponding to the vehicle speed V. The vehicle speed gain is set to a larger value as the vehicle speed V becomes faster. Since the behavior of the vehicle is reflected in the yaw rate YR, the behavior of the vehicle is also reflected in the yaw rate axial force AF ₅ calculated based on the yaw rate YR. Further, since the yaw rate axial force AF ₅ is calculated based on the yaw rate YR, it is not easily affected by the current limitation of the steering motor 41. Therefore, even when the yaw rate axial force calculation unit 81H is provided instead of the lateral G axial force calculation unit 81G, the same effect as when the lateral G axial force calculation unit 81G is provided can be obtained.

(9) Further, depending on the product specifications and the like, a configuration in which the angle axial force calculation unit 81A is omitted may be adopted as the axial force calculation unit 72. When this configuration is adopted, the distribution ratio calculation unit 81E reduces the degree of reflection of the current axial force AF ₂ on the final axial force AF ₃ when a specific situation occurs in which the current _Ib of the steering motor 41 should be limited. On the other hand, the values of the distribution ratios DR ₂ and DR ₄ for the current limitation are calculated so that the degree of reflection of the lateral G-force AF ₄ with respect to the final axial force AF ₃ increases. Therefore, it is possible to prevent the current limit of the steering motor 41 from affecting the steering reaction force.

<7th embodiment>
Next, a seventh embodiment in which the steering control device is embodied in a steer-by-wire type steering device will be described. This embodiment basically has the same configuration as that of the second embodiment. This embodiment is different from the first embodiment in that the axial force calculation unit 72 is configured.

As shown in FIG. 6, the axial force calculation unit 72 has the same configuration as that of the second embodiment, that is, in addition to the angle axial force calculation unit 81A, the current axial force calculation unit 81B, the converter 81D, and the switch 81F. It also has a lateral G-axis force calculation unit 81G.

When the value of the flag F is "0", the switch 81F selects the current axial force AF ₂ calculated by the current axial force calculation unit 81B as the final axial force AF ₃ . When the value of the flag F is "1", the switch 81F has an angular axial force AF ₁ calculated by the angular axial force calculation unit 81A or a lateral G-axis force AF ₄ calculated by the lateral G-axis force calculation unit 81G. Is selected as the final axial force AF ₃ . However, the axial force selected when the value of the flag F is "1" is determined by the product specifications.

Therefore, according to the seventh embodiment, the following effects can be obtained.
(10) When a specific situation occurs in which the current I _b of the steering motor 41 should be limited, the current axial force AF ₂ calculated based on the current I _b of the steering motor 41 is not used. That is, as the final axial force AF ₃ which is the final axial force reflected in the steering reaction force command value T ^* by the angular axial force AF ₁ or the lateral G axial force AF ₄ which is not affected by the current limitation of the steering motor 41. It is calculated. Therefore, even when the current of the steering motor 41 is limited, it is possible to secure the steering reaction force as information for the driver.

(11) Further, when a specific situation occurs in which the current _Ib of the steering motor 41 should be limited, the axial force reflected in the steering reaction force command value T ^* is simply changed by switching the switch 81F, and the current axial force AF ₂ Can be switched from to the angular axial force AF ₁ or the lateral G axial force AF ₄ . Therefore, it is possible to reduce the calculation load of the control device 50.

(12) Incidentally, depending on the product specifications and the like, a configuration in which the angle axial force calculation unit 81A is omitted may be adopted as the axial force calculation unit 72. When this configuration is adopted, the lateral G-force AF ₄ is calculated as the final axial force AF ₃ when a specific situation occurs in which the current _Ib of the steering motor 41 should be limited. The lateral G-force AF ₄ is not easily affected by the current limitation of the steering motor 41. Therefore, even when the current of the steering motor 41 is limited, it is possible to secure the steering reaction force as information for the driver.

(13) As shown in FIG. 6 with reference numerals in parentheses, a yaw rate axial force calculation unit 81H may be provided instead of the lateral G-axis force calculation unit 81G. When this configuration is adopted, when a specific situation occurs in which the current _Ib of the steering motor 41 should be limited, the angular axial force AF ₁ or the yaw rate axial force AF ₅ is calculated as the final axial force AF ₃ . The yaw rate axial force AF ₅ is not easily affected by the current limitation of the steering motor 41. Therefore, even when the current of the steering motor 41 is limited, it is possible to secure the steering reaction force as information for the driver.

<8th embodiment>
Next, an eighth embodiment in which the steering control device is embodied in a steer-by-wire type steering device will be described. This embodiment basically has the same configuration as the first embodiment shown in FIGS. 1 to 3 above. Further, in the present embodiment, as in the third embodiment described above, a plurality of situations are assumed as situations in which the current of the steering motor 41 should be limited.

The reaction force control unit 50a and the steering control unit 50b of the control device 50 are provided as separate electronic control units (ECUs) independent of each other. The reaction force control unit 50a and the steering control unit 50b exchange information with each other via an in-vehicle network such as a CAN (Controller Area Network).

The limit control unit 64 detects the temperature _Tm of the steering motor 41 through the temperature sensor 62a. The limit control unit 64 determines the heat generation state of the steering motor 41 by comparing the temperature _Tm of the steering motor 41 with a plurality of temperature threshold values. The heat generation state of the steering motor 41 includes a normal heat generation state in which heat is not generated to the extent that the current of the steering motor 41 is limited, a mild overheating state, a moderate overheating state, and a severe overheating state. The limit control unit 64 calculates a limit value _Ilim having a smaller absolute value as the degree of overheating of the steering motor 41 increases.

Further, the limit control unit 64 detects the voltage V _b of the DC power supply through the voltage sensor 502. The limit control unit 64 determines the state of the voltage of the DC power supply by comparing the voltage V _b of the DC power supply with a plurality of voltage threshold values. The voltage state of the DC power supply includes a normal voltage state in which the voltage does not drop enough to limit the current of the steering motor 41, a slight voltage drop state, a moderate voltage drop state, and a severe voltage drop state. included. The limit control unit 64 calculates a limit value _Ilim having a smaller absolute value as the degree of voltage drop of the DC power supply increases.

The limitation control unit 64 executes the following processing instead of setting the value of the flag F indicating whether or not the current amount of the steering motor 41 should be limited. That is, the restriction control unit 64 encodes the state of the steering device 10 according to the code table stored in the storage device of the control device 50. The coding means a process of expressing the state of the steering device 10 with a code as a symbol. The state of the steering device 10 includes a heat generation state of the steering motor 41 and a voltage state of the DC power supply. An example of the correspondence between the state of the steering device 10 and the cord is as follows.

-Code "0" ... Normal state where the current of the steering motor 41 is not limited-Code "1A" ... Mild overheating state of the steering motor 41-Code "1B" ... Medium overheating state of the steering motor 41- Code "1C" ... Severe overheating state of steering motor 41-Code "2A" ... Slight voltage drop state of DC power supply-Code "2B" ... Moderate voltage drop state of DC power supply-Code "2C" ... DC Severe voltage drop state of the power supply The steering control unit 50b transmits the code set by the limitation control unit 64 to the reaction force control unit 50a via the vehicle-mounted network. The reaction force control unit 50a receives a code via the vehicle-mounted network, and executes reaction force control according to the received code. For example, the reaction force control unit 50a changes the value of the distribution ratio DR ₁ of the angle axial force AF ₁ and the value of the distribution ratio DR ₂ of the current axial force AF ₂ according to the code as a part of the reaction force control. For example, the distribution ratio calculation unit 81E changes the values of the two distribution ratios DR ₁ and DR ₂ step by step according to the degree of the situation in which the current of the steering motor 41 grasped from the code should be limited.

When the steering motor 41 is in an overheated state, the distribution ratio calculation unit 81E deteriorates the overheated state in the order of "mild", "moderate", and "severe", so that the distribution ratio DR of the angular axial force AF ₁ becomes worse. The value of ₁ is set to a larger value, while the value of the distribution ratio DR ₂ of the current axial force AF ₂ is set to a smaller value. However, the two distribution ratios DR ₁ and DR ₂ for the current limit are set so that the total of them is "1 (100%)". Further, the two distribution ratios DR1 and DR2 for the time of current limitation are set to appropriate values depending on the product specifications and the like. Specific setting examples of the two distribution ratios DR ₁ and DR ₂ are as follows.

When the code "1A" is acquired, that is, when the heat generation state of the steering motor 41 is a slight overheating state, the distribution ratio calculation unit 81E has two, as represented by the following relational expression (8). Distribution ratio Set the values of DR ₁ and DR ₂ .

DR ₁ : DR ₂ = 0.8 (80%): 0.2 (20%) ... (8)
When the code "1B" is acquired, that is, when the heat generation state of the steering motor 41 is a moderately overheated state, the distribution ratio calculation unit 81E has 2 as expressed by the following relational expression (9). Set the values of the two distribution ratios DR ₁ and DR ₂ .

DR ₁ : DR ₂ = 0.9 (90%): 0.1 (10%) ... (9)
When the code "1C" is acquired, that is, when the heat generation state of the steering motor 41 is a severe overheat state, the distribution ratio calculation unit 81E has two, as represented by the following relational expression (10). Distribution ratio Set the values of DR ₁ and DR ₂ .

DR ₁ : DR ₂ = 1 (100%): 0 (0%) ... (10)
When the voltage V _b of the DC power supply decreases, the distribution ratio calculation unit 81E distributes the angular axial force AF ₁ so that the degree of decrease deteriorates in the order of “mild”, “moderate”, and “severe”. The value of the ratio DR ₁ is set to a larger value, while the value of the distribution ratio DR ₂ of the current axial force AF ₂ is set to a smaller value. However, the two distribution ratios DR ₁ and DR ₂ for the current limit are set so that the total of them is "1 (100%)". Further, the two distribution ratios DR1 and DR2 for the time of current limitation are set to appropriate values depending on the product specifications and the like. Specific setting examples of the two distribution ratios DR ₁ and DR ₂ are as follows.

When the code "2A" is acquired, that is, when the state of the DC power supply is a slight voltage drop state, the distribution ratio calculation unit 81E has two distribution ratios as represented by the following relational expression (11). Set the values of DR ₁ and DR ₂ .

DR ₁ : DR ₂ = 0.8 (80%): 0.2 (20%) ... (11)
When the code "2B" is acquired, that is, when the DC power supply is in a moderate voltage drop state, the distribution ratio calculation unit 81E has two distributions as represented by the following relational expression (12). Set the values of the ratios DR ₁ and DR ₂ .

DR ₁ : DR ₂ = 0.9 (90%): 0.1 (10%) ... (12)
When the code "2C" is acquired, that is, when the state of the DC power supply is a severe voltage drop state, the distribution ratio calculation unit 81E has two distribution ratios as represented by the following relational expression (13). Set the values of DR ₁ and DR ₂ .

DR ₁ : DR ₂ = 1 (100%): 0 (0%) ... (13)
Incidentally, it is conceivable that a plurality of situations in which the current of the steering motor 41 should be limited, in which the overheating of the steering motor 41 and the voltage drop of the DC power supply occur at the same time. Based on the viewpoint corresponding to such a situation, the code may be prioritized according to, for example, the type or degree of the state of the steering device 10. For example, the code "1C" indicating a severe overheating state of the steering motor 41 is prioritized over the code "2A" indicating a slight voltage drop state of the DC power supply.

Therefore, according to the eighth embodiment, the following effects can be obtained.
(14) The steering control unit 50b transmits a code, which is a symbol indicating the state of the steering device 10, to the reaction force control unit 50a. Therefore, when information such as the temperature _Tm of the steering motor 41 and the voltage V _b of the DC power supply acquired by the steering control unit 50b is transmitted to the reaction force control unit 50a as information indicating the state of the steering device 10 as it is. In comparison, the communication load between the reaction force control unit 50a and the steering control unit 50b is reduced.

(15) The distribution ratio of the angular axial force AF ₁ depends on the degree of a specific situation in which the current _Ib of the steering motor 41 should be limited, for example, the degree of overheating of the steering motor 41 or the degree of voltage drop of the DC power supply. Increase or decrease the value of DR ₁ and the value of the distribution ratio DR ₂ of the current axial force AF ₂ . Thereby, it is possible to gradually switch between the angular axial force AF ₁ and the current axial force AF ₂ according to the degree of a specific situation in which the current _Ib of the steering motor 41 should be limited. Therefore, it is possible to gradually secure the steering reaction force as information for the driver according to the degree of the specific situation in which the current _Ib of the steering motor 41 should be limited.

<Other embodiments>
The first to eighth embodiments may be modified as follows.
In the first to eighth embodiments, the angle axial force calculation unit 81A is calculated by the steering angle θ _s calculated by the steering angle calculation unit 51 or the target pinion angle calculation unit 62 instead of the pinion angle θ _p . The angle axial force AF ₁ may be calculated based on the target pinion angle θ _p ^* . The angular axial force AF ₁ calculated in this way is also an ideal value of the axial force acting on the steering shaft 14 according to the steering state.

In the first to seventh embodiments, the reaction force control unit 50a and the steering control unit 50b in the control device 50 may be configured as separate electronic control units (ECUs) independent of each other.
-In the first to eighth embodiments, the steering device 10 may be provided with a clutch. In this case, as shown by the alternate long and short dash line in FIG. 1, the steering shaft 12 and the pinion shaft 13 are connected via the clutch 21. As the clutch 21, an electromagnetic clutch that engages and disengages power through disengagement of energization of the exciting coil is adopted. The control device 50 executes intermittent control for switching the engagement and disengagement of the clutch 21. When the clutch 21 is disengaged, the power transmission between the steering wheel 11 and the steering wheel 16 is mechanically disengaged. When the clutch 21 is engaged, the power transmission between the steering wheel 11 and the steering wheel 16 is mechanically coupled.

11 ... Steering wheel 14 ... Steering shaft 31 ... Reaction force motor 41 ... Steering motor 50 ... Control device (steering control device)
50a ... Reaction force control unit 50b ... Steering control unit 81A ... Angle axial force calculation unit (second calculation unit)
81B ... Current axial force calculation unit (first calculation unit)
81C ... Axial force distribution calculation unit (third calculation unit)
81E ... Distribution ratio calculation unit (fourth calculation unit)
81F ... Switch (third arithmetic unit)
81G ... Lateral G-force calculation unit (second calculation unit)
81H ... Yaw rate axial force calculation unit (second calculation unit)

Claims (6)

It is a steering control device that controls the reaction force motor, which is the source of the steering reaction force applied to the steering wheel separated from the steering shaft, based on the command value calculated according to the steering state. hand,
A first calculation unit that calculates a first axial force acting on the steering shaft based on a current value of a steering motor that is a source of a steering force applied to the steering shaft.
A second calculation unit that calculates a second axial force acting on the steering shaft based on other vehicle state variables different from the current value of the steering motor.
A third calculation unit for calculating a third axial force, which is the final axial force to be reflected in the command value based on the first axial force and the second axial force, is provided.
The third calculation unit reduces the degree of reflection of the first axial force on the third axial force when a specific situation in which the current of the steering motor should be limited occurs, while the third calculation unit reduces the degree of reflection of the first axial force on the third axial force. A steering control device that increases the degree of reflection of the second axial force on the axial force of the above. The third calculation unit adds up the values obtained by multiplying the first axial force and the second axial force by a distribution ratio individually set according to the vehicle behavior, steering state, or road surface condition. The third axial force is calculated by
The third arithmetic unit reduces the distribution ratio of the first axial force to the third axial force when a specific situation occurs in which the current of the steering motor should be limited, while the third calculation unit reduces the distribution ratio of the first axial force to the third axial force. The steering control device according to claim 1, wherein the distribution ratio of the second axial force to the axial force of the above is increased. When a specific situation occurs in which the current of the steering motor should be limited, the distribution ratio of the first axial force to the third axial force is further reduced, while the second axial force to the third axial force is further reduced. It has a fourth calculation unit for individually calculating the distribution ratio for the current limitation to the first axial force and the second axial force from the viewpoint of further increasing the distribution ratio of the axial force of the above.
The third arithmetic unit uses the current limiting distribution ratio calculated by the fourth arithmetic unit when a specific situation occurs in which the current of the steering motor should be limited. The steering control device according to claim 2, wherein the axial force of the vehicle is calculated. The fourth calculation unit sets the distribution ratio of the first axial force to the third axial force to 0% when a specific situation occurs in which the current of the steering motor should be limited. The steering control device according to claim 3, wherein the distribution ratio of the second axial force to the third axial force is set to 100%. The third calculation unit calculates the first axial force as it is as the third axial force when a specific situation in which the current of the steering motor should be limited does not occur.
The steering control device according to claim 1, wherein when a specific situation for limiting the current of the steering motor occurs, the second axial force is calculated as it is as the third axial force. A steering control unit that controls the steering motor according to a steering state is included.
The steering control unit sets the value of a flag indicating whether or not a specific situation in which the current of the steering motor should be limited has occurred based on whether or not the predetermined determination condition is satisfied.
The third calculation unit recognizes that a specific situation has occurred in which the current of the steering motor should be limited based on the value of the flag set by the steering control unit. The steering control device according to any one of the above.

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